Takeuchi, Yutaro*; Yamane, Yuta*; Yoon, J.-Y.*; Ito, Ryuichi*; Jinnai, Butsurin*; Kanai, Shun*; Ieda, Junichi; Fukami, Shunsuke*; Ono, Hideo*
Nature Materials, 20(10), p.1364 - 1370, 2021/10
Qiu, Z.*; Hou, D.*; Barker, J.*; Yamamoto, Kei; Gomonay, O.*; Saito, Eiji*
Nature Materials, 17(7), p.577 - 580, 2018/05
Colossal magnetoresistance (CMR) refers to a large change in electrical conductivity induced by a magnetic field in the vicinity of a metal-insulator transition. CMR occurs due to a correlation between the magnetic structure and electron conduction and has inspired extensive studies for decades. Here, in the antiferromagnetic insulator CrO, we found a sharp transition between conducting and nonconducting states for spin currents at room temperature. The spin-current transmission changes by two orders of magnitude within a narrow temperature window of 14K around the Neel temperature. The spin conductor-nonconductor transition can be modulated by a magnetic field, giving an isothermal change of spin-current transmission of up to 500%, effectively an on-off switch for spin currents.
Li, B.; Wang, H.*; Kawakita, Yukinobu; Zhang, Q.*; Feygenson, M.*; Yu, H. L.*; Wu, D.*; Ohara, Koji*; Kikuchi, Tatsuya*; Shibata, Kaoru; et al.
Nature Materials, 17(3), p.226 - 230, 2018/03
Christle, D.*; Falk, A.*; Andrich, A.*; Klimov, P.*; Hassan, J.*; Son, N. T.*; Janzn, E.*; Oshima, Takeshi; Awschalom, D.*
Nature Materials, 14(2), p.160 - 163, 2015/02
Widmann, M.*; Lee, S.-Y.*; Rendler, T.*; Son, N. T.*; Fedder, H.*; Paik, S.*; Yang, L.-P.*; Zhao, N.*; Yang, S.*; Booker, I.*; et al.
Nature Materials, 14(2), p.164 - 168, 2015/02
Okamoto, Naoya*; Kurebayashi, Hidekazu*; Trypiniotis, T.*; Farrer, I.*; Ritchie, D. A.*; Saito, Eiji; Sinova, J.*; Maek, J.*; Jungwirth, T.*; Barnes, C.*
Nature Materials, 13(10), p.932 - 937, 2014/10
Castelletto, S.*; Johnson, B.*; Ivady, V.*; Stavrias, N.*; Umeda, Takahide*; Gali, A.*; Oshima, Takeshi
Nature Materials, 13(2), p.151 - 156, 2014/02
The generation and detection of single photons play a central role in the experimental foundation of quantum mechanics and measurement theory. An effcient and high-quality single-photon source is thought to be necessary to realize quantum key distribution, quantum repeaters and photonic quantum information processing. We found the identication and formation of ultra-bright, room temperature, photo-stable single photon sources in silicon carbide (SiC). The single photon source consists of an intrinsic defect which is known as the carbon antisite vacancy pair, created by carefully optimized electron irradiation and annealing of ultra pure SiC. An extreme brightness (210 counts/s) resulting from polarization rules and a high quantum effciency is obtained in the bulk without resorting to the use of a cavity or plasmonic structure.
Ando, Kazuya*; Watanabe, Shun*; Mooser, S.*; Saito, Eiji; Sirringhaus, H.*
Nature Materials, 12(7), p.622 - 627, 2013/07
We show that a pure spin current can be produced in a solution-processed conducting polymer by pumping spins through a ferromagnetic resonance in an adjacent magnetic insulator, and that this generates an electric voltage across the polymer film. We demonstrate that the experimental characteristics of the generated voltage are consistent with it being generated through an inverse spin Hall effect in the conducting polymer. In contrast with inorganic materials, the conducting polymer exhibits coexistence of high spin-current to charge-current conversion efficiency and long spin lifetimes. Our discovery opens a route for a new generation of molecular-structure-engineered spintronic devices, which could lead to important advances in plastic spintronics.
An, Toshu*; Vasyuchka, V. I.*; Uchida, Kenichi*; Chumak, A. V.*; Yamaguchi, Kazuya*; Harii, Kazuya; Oe, Junichiro*; Jungfleisch, M. B.*; Kajiwara, Yosuke*; Adachi, Hiroto; et al.
Nature Materials, 12(6), p.549 - 553, 2013/06
Kirihara, Akihiro*; Uchida, Kenichi*; Kajiwara, Yosuke*; Ishida, Masahiko*; Nakamura, Yasunobu*; Manako, Takashi*; Saito, Eiji; Yorozu, Shinichi*
Nature Materials, 11(8), p.686 - 689, 2012/08
Bauer, G. E. W.*; Saito, Eiji; Van Wees, B. J.*
Nature Materials, 11(5), p.391 - 399, 2012/05
Spintronics is about the coupled electron spin and charge transport in condensed-matter structures and devices. The recently invigorated field of spin caloritronics focuses on the interaction of spins with heat currents, motivated by newly discovered physical effects and strategies to improve existing thermoelectric devices. Here we give an overview of our understanding and the experimental state-of-the-art concerning the coupling of spin, charge and heat currents in magnetic thin films and nanostructures. Known phenomena are classified either as independent electron (such as spin-dependent Seebeck) effects in metals that can be understood by a model of two parallel spin-transport channels with different thermoelectric properties, or as collective (such as spin Seebeck) effects, caused by spin waves, that also exist in insulating ferromagnets. The search to find applications - for example heat sensors and waste heat recyclers - is on.
Uchida, Kenichi*; Adachi, Hiroto; An, Toshu*; Ota, Takeru*; Toda, Masaya*; Hillebrands, B.*; Maekawa, Sadamichi; Saito, Eiji
Nature Materials, 10(10), p.737 - 741, 2011/10
We show that, using a NiFe/Pt bilayer wire on an insulating sapphire plate, electrons in the wire recognize their position on the sapphire. Under a temperature gradient in the sapphire, surprisingly, the voltage generated in the Pt layer is shown to reflect the wire position, although the wire is isolated both electrically and magnetically. This non-local voltage due to the coupling of spins and phonons: the only possible carrier of information in this system. We demonstrate this coupling by directly injecting sound waves, which realizes the acoustic spin pumping. Our finding provides a persuasive answer to the long-range nature of the spin Seebeck effect, and it opens the door to "acoustic spintronics" in which sound waves are exploited for constructing spin-based devices.
Ando, Kazuya*; Takahashi, Saburo; Ieda, Junichi; Kurebayashi, Hidekazu*; Trypiniotis, T.*; Barnes, C. H. W.*; Maekawa, Sadamichi; Saito, Eiji
Nature Materials, 10(9), p.655 - 659, 2011/09
Fukuma, Yasuhiro*; Le, W.*; Izuchi, Hiroshi*; Takahashi, Saburo; Maekawa, Sadamichi; Otani, Yoshichika*
Nature Materials, 10(7), p.527 - 531, 2011/07
Uchida, Kenichi*; Xiao, J.*; Adachi, Hiroto; Oe, Junichiro; Takahashi, Saburo; Ieda, Junichi; Ota, Takeru*; Kajiwara, Yosuke*; Umezawa, Hiromitsu*; Kawai, Hirotaka*; et al.
Nature Materials, 9(11), p.894 - 897, 2010/11
Thermoelectric generation is an essential function in future energy-saving technologies. However, it has so far been an exclusive feature of electric conductors, a situation which limits its application; conduction electrons are often problematic in the thermal design of devices. Here we report electric voltage generation from heat flowing in an insulator. We reveal that, despite the absence of conduction electrons, the magnetic insulator LaYFeO can convert a heat flow into a spin voltage. Attached Pt films can then transform this spin voltage into an electric voltage as a result of the inverse spin Hall effect. The experimental result require us to introduce a thermally activated interface spin exchange between LaYFeO and Pt. Our findings extend the range of potential materials for thermoelectric applications and provide a crucial piece of information for understanding the physics of the spin Seebeck effect.
Yang, H.*; Yang, S.-H.*; Takahashi, Saburo; Maekawa, Sadamichi; Parkin, S.*
Nature Materials, 9(7), p.586 - 593, 2010/07
There has been an intense search in recent years for long-lived spin-polarized carriers for spintronic and quantum-computing devices. Here we report that spin polarized quasi-particles in superconducting aluminum layers have surprisingly long spin-lifetimes, nearly a million times longer than in their normal state. The lifetime is determined from the suppression of the aluminum's superconductivity resulting from the accumulation of spin polarized carriers in the aluminum layer using tunnel spin injectors. A Hanle effect, observed in the presence of small in-plane orthogonal fields, is shown to be quantitatively consistent with the presence of long-lived spin polarized quasi-particles. Our experiments show that the superconducting state can be significantly modified by small electric currents, much smaller than the critical current, which is potentially useful for devices involving superconducting qubits.
de Boissieu, M.*; Francoual, S.*; Minalkovi, M.*; Shibata, Kaoru; Baron, A. Q. R.*; Sidis, Y.*; Ishimasa, Tsutomu*; Wu, D.*; Lograsso, T.*; Regnault, L.-P.*; et al.
Nature Materials, 6(12), p.977 - 984, 2007/12
We have carried out inelastic X-ray and neutron scattering experiments on single-grain samples of the Zn-Mg-Sc icosahedral quasicrystal and of the Zn-Sc periodic cubic 1/1 approximant, with the aim of studying the respective influence of the local order and the long-range order (periodic or quasiperiodic) on lattice dynamics. Besides the overall similarities and the existence of a pseudo-gap in the transverse dispersion relation, marked difference are observed, the pseudo-gap being larger and better defined in the approximant than in the quasicrystal. These results are compared with simulations on atomic models and using oscillating pair potentials, and the simulations reproduce in detail the experimental results.
Lee, S.*; Park, J.-G.*; Adroja, D. T.*; Khomskii, D.*; Streltsov, S.*; McEwen, K. A.*; Sakai, Hironori; Yoshimura, Kazuyoshi*; Anisimov, V. I.*; Mori, Daisuke*; et al.
Nature Materials, 5(6), p.471 - 476, 2006/06
Here we show that the three-dimensional cubic system of TlRuO most probably evolves into a one-dimensional spin-one Haldane system with a spin gap below 120 K, accompanied by anomalies in the structure, resistivity, and susceptibility. We argue that these anomalies are due to an orbital ordering of Ru electrons, with a strong coupling among three degrees of freedom: orbital, spin, and lattice. Our work provides a unique example of the spontaneous formation of Haldane system with an insight into the intriguing interplay of different degrees of freedom.
Utsumi, Wataru; Saito, Hiroyuki; Kaneko, Hiroshi*; Watanuki, Tetsu; Aoki, Katsutoshi; Shimomura, Osamu
Nature Materials, 2(11), p.735 - 738, 2003/11
Synthesis of large single crystal GaN (gallium nitride) is a matter of great importance in optoelectronic devices for blue light-emitting diodes and lasers. Although high quality bulk single crystals of GaN suitable for substrates are desired, the standard method of cooling its stoichiometric melt has been unsuccessful for GaN because it decomposes into Ga and N at high temperatures before its melting point. Here we report that applying high pressure completely prevents the decomposition and allows the stoichiometric melt of GaN. At pressures above 6.0 GPa, congruent melting of GaN occurred around 2220C, and decreasing the temperature allowed the GaN melt to reversibly back-transform into the original crystal structure, which was confirmed by in situ X-ray diffraction. Single crystals of GaN were formed by cooling the melt slowly under high pressures and were recovered at ambient conditions.